Cathode ray tube electron gun

ABSTRACT

In a cathode ray tube electron gun, a dimensional stability, is provided for capping a terminal-emitting cathode sleeve. The cathode closure is diversely shaped to have a mesa-like terminal portion, with the planar end surface therof formed to provide a flat substrate area to accommodate the deposition of electron emissive material thereon. A strengthening transition portion extends from the periphery of the mesa-like portion to form an annular shoulder therearound. A peripheral skirt portion, extending downward from the shoulder, is of a length and internal diameter to facilitate encompassment and affixation to the terminal portion of the sleeve.

Related 0.8. Application Data United States Patent [191' [111 3,763,388 Benda Oct. 2, 1973 1 CATl-IODE RAY TUBE ELECTRON GUN Primary ExaminerRudolph v. Rolinec Assistant Examiner-Wm H. Punter [75] Inventor. David Benda,Geneva,N.Y. Atwmey Norman J. OMaHey et a].

[73] Assignee: GTE Sylvania Incorporated,

Seneca Falls, NY. [571 ABSTRACT In a cathode ray tube electron gun, a dimensional sta- [22] Flled' O 1972 bility, is provided for capping a terminal-emitting cath- [21] Appl. No.: 302,358 ode sleeve. The cathode closure is diversely shaped to have a mesa-like terminal portion, with the planar end surface therof formed to provide a flat substrate area to accommodate the deposition of electron emissive material thereon. A strengthening transition portion extends from the periphery of the mesa-like portion to form an annular shoulder therearound. A peripheral skirt portion, extending downward from the shoulder, is of a length and internal diameter to facilitate encompassment and affixation to the terminal portion of the sleeve.

3 Claims, 3 Drawing Figures PATENTEDUBT 21973 CATHODE RAY TUBE ELECTRON GUN CROSS-REFERENCE TO RELATED APPLICATION This application is a divisional application of Ser. No. 190,599, filed Oct. 19, 1971, now U.S. Pat. No. 3,728,574 and assigned to the assignee of the present invention. Recorded Oct. 19, 1971, Reel 2802, Frame 659.

BACKGROUND OF THE INVENTION This invention relates to cathode ray tube electron guns employing terminal-emitting thermionic cathodes and more particularly to a gun utilizing a cathode cap exhibiting improved dimensional stability.

Terminal closures for end-emitting cathodes in CRT electron guns are conventionally formed as cup-like structures each having a flat or planar surface with a surrounding wall or skirt portion extending peripher ally therefrom. The planar surface provides a substrate for an area coating of thermionic emissive material, and the skirt portion is of a length and diameter to facilitate affixation to the upper end portion of a cathode sleeve. It is usual procedure to assemble and attach the cap to the sleeve by two or more welds effected in the skirt area. Due to a relationship of manufacturing tolerances, the welding procedure often effects a pull-in of the skirt, particularly in the areas of the several welds, which in turn produces a degree of deleterious distortion of the planar end surface. Since it is important that the substrate surface be free of distortion, it has been usual practice to subject the integrated cap-sleeve assembly to a pressured-sizing operation, whereby a rodlike anvil is inserted into the sleeve to provide a flattening procedure which restores the desired planar surface to the end portion of the cap. This corrective operation is not only time consuming and an added fabricating expense, but it is also a source of unwanted contamination which must be removed from the substrate region before the emissive material is applied thereon, otherwise, the desired operational life and level of the subse quently initiated electron emission would be jeopardized.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide a cathode ray tube electron gun having an improved cathode cap that is formed to have improved dimensional stability. A further object is to provide an electron gun having a cathode cap that has a planar substrate surface that is minimally affected by cap-to-sleeve affixation means.

The foregoing objects are achieved in one aspect of the invention by providing an improved closure portion for capping a thermionic terminal-emitting cathode ray tube cathode sleeve. The closure cap, which exhibits improved dimensional stability is shaped to have a mesa-like tenninal portion whereof the planar end surface provides a substrate upon which a coating of electron emissive material is subsequently disposed. Ex-

tending peripherally outward from the base of the BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged partial sectional showing orientation of the invention relative to the cathode sleeve, the shield, and the control grid in a cathode ray tube electron gun;

FIG. 2 is an enlarged view of the improved cathode cap; and

FIG. 3 is a plan view of the improved cap taken along the line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the afore-described drawings.

With reference to FIG. 1 there is shown an enlarged sectional view illustrating part of a cathode ray tube electron gun l1 spacially oriented by means, not shown, within the tubular neck portion 13 of a cathode ray tube envelope. The exemplary electron gun structure 11 is comprised of a number of electrodes, one of which is a control grid 15 having an aperture 17 therein. Control grid support means 19 are appropriately embedded in the electron gun insulative'support rods 21. Positioned adjacent the control grid 15 is a cathode assembly 23, comprising for example, a cathode shielding eyelet 25, a substantially cylindrical cathode sleeve 27, and a terminally attached improved closure cap 29. The end or planar terminal surface 31 of the cap forms a flat substrate for the thermionic electron emissive coating 33. A cathode assembly support member 35 is embedded in the gun insulative support rods 21 to provide the proper spatial relationship between the emissive material 33 and the control grid aperture 17. It is to be noted that the aforedescribed cathode placement and support means is not to be considered limiting. A conventional heater 37 is positioned by support means 38 within the cathode sleeve 27 through the open end 39 thereof to provide the necessary operational heat thereto to promote the desired thermionic emission from the emissive material 33.

To describe the improved cathode cap 29, reference is made to FIGS. 2 and 3 in particular, wherein the cap structure is shown in greater detail. This closure cap is made of a conven-tional nickel or nickel alloy material that is promotive of thermionic electron emission, and as such, provides a proper substrate for the subsequently applied emissive coating 33, as shown in FIG. 1. The cap is formed to encompass the end portion of the metallic cathode sleeve 27 and be attached or-affixed thereto as by a plurality of welds or bonds 41.

The improved closure cap 29 is structurally shaped to have a substantially circular mesa-like terminal portion 43 that is formed of an upstanding wall 45 topped by the substantially planar end or substrate surface 31. A strengthening transition portion 47 extends integrally from the periphery of the base 49 of the upstanding wall 45 to form a substantially outstanding annular shoulder portion thereabove. While not essential, it is preferable that the wall 45 and the annular shoulder portion 47 form a substantially right angle 0 relationship therebetween to clearly define the mesa-like structure; with the plane of the substrate surface 31 being substantially parallel with the plane of the annular shoulder portion 47. A skirt portion 51 extends from the outer periphery 53 of the shoulder portion 47 in a downward directional manner opposed to the mesa-like portion 43. The skirt portion 51 has an internal diameter a of a dimensional tolerance slightly larger than the external diameter b of the cathode sleeve 27 to facilitate fitted terminal encompassment of the sleeve.

The formed structure of the cap is advantageous in maintaining dimensional stability during cathode assembly and subsequent operation. The relationship between the transition portion 47 and the upstanding wall 45 of the terminal portion 43 provides a stabilizing hinge-effect therebetween; the apex of the right angle being formed with as small a radius as possible at the wall periphery 49 to promote hinging action. By this structure, any movement of the skirt, such as occasioned by welding, is minimized in the substrate region 31 by the movement absorbing linkage effected by the aforedescribed angular arrangement. The annular shoulder 47 and the adjoining wall 45 have also been found to be advantageous in fabrication of the sleevecap assembly, in that, any placement pressure necessary to position the cap 29 on the end portion of the sleeve 27 can be discretely directed or applied to the shoulder area 47 rather than against the critical planar substrate surface 31.

As shown in FIG. 2, the mesa-like terminal construction 43 is additionally advantageous in that it can be utilized to center the heater 37' within the cathode cap 29 thereby promoting a uniformity of temperature distribution in particularly the terminal portion of the cap. When such discrete placement is desired, the internal periphery 50 of the mesa portion 43 and the end shaping of the heater 37' are compatibly dimensioned to provide guided and supportive centralized positioning of the heater relative to the planar surface 31 of the cap.

To facilitate assembly of the cap 29 onto the end of the sleeve 27, a slight outward annular flare 59 is circumferentially formed about the edge of the skirt portion 51.

Thus, there is provided an electron gun having an improved cathode closure cap that has enhanced dimensional stability, and one wherein the terminal planar substrate surface is minimally affected by movement of the skirt during cap-to-sleeve attachment.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. In a cathode ray tube electron gun oriented in the tube neck portion, a cathode and control grid relationship comprising:

a substantially cylindrical supportive cathode sleeve;

a closure cap formed to encompass the terminal portion of said cathode sleeve, said cap having a substantially circular mesa-like terminal portion formed of an upstanding wall extending from an annular portion normal thereto and topped by a substantially planar end surface providing a flat substrate area, a strengthening transition portion extends from the periphery of the base of said mesa-like portion to form an outstanding annular shoulder portion thereabout, a skirt portion extends from the outer periphery of the shoulder portion in a manner opposed to the mesa-like portion to facilitate fitted telescopic encompassment and plural bond affixation to the terminal sidewall portion of said sleeve;

an area of electron emissive material disposed on said flat substrate surface of said cathode closure cap;

cathode heater means positioned within said sleeve to provide heat for said electron emissive material to effect thermionic emission therefrom;

a control grid having an aperture therein positioned adjacent said cathode emissive surface in a manner to control the electron emission therefrom; and

support means for individually positioning said capped-cathode, said heater, and said control grid in insulative relationship with one another.

2. In a cathode ray tube electron gun according to claim 1 wherein the mesa-like portion of said cap is internally dimensioned to accommodate the guided and supportive centralized positioning of said heater relative to the planar surface of said closure cap.

3. In a cathode ray tube electron gun according to claim 1 wherein the upstanding wall of said mesa-like terminal portion of said cathode closure cap forms a substantially right angle with said annular shoulder portion thereabout, said right angle relationship having a small radius to provide a hinge effect to insure the flatness of said terminal substrate area.

* s k a: 

1. In a cathode ray tube electron gun oriented in the tube neck portion, a cathode and control grid relationship comprising: a substantially cylindrical supportive cathode sleeve; a closure cap formed to encompass the terminal portion of said cathode sleeve, said cap having a substantially circular mesalike terminal portion formed of an upstanding wall extending from an annular portion normal thereto and topped by a substantially planar end surface providing a flat substrate area, a strengthening transition portion extends from the periphery of the base of said mesa-like portion to form an outstanding annular shoulder portion thereabout, a skirt portion extends from the outer periphery of the shoulder portion in a manner opposed to the mesa-like portion to facilitate fitted telescopic encompassment and plural bond affixation to the terminal sidewall portion of said sleeve; an area of electron emissive material disposed on said flat substrate surface of said cathode closure cap; cathode heater means positioned within said sleeve to provide heat for said electron emissive material to effect thermionic emission therefrom; a control grid having an aperture therein positioned adjacent said cathode emissive surface in a manner to control the electron emission therefrom; and support means for individually positioning said capped-cathode, said heater, and said control grid in insulative relationship with one another.
 2. In a cathode ray tube electron gun according to claim 1 wherein the mesa-like portion of said cap is internally dimensioned to accommodate the guided and supportive centralized positioning of said heater relative to the planar surface of said closure cap.
 3. In a cathode ray tube electron gun according to claim 1 wherein the upstanding wall of said mesa-like terminal portion of said cathode closure cap forms a substantially right angle with said annular shoulder portion thereabout, said right angle relationship having a small radius to provide a hinge effect to insure the flatness of said terminal substrate area. 